The goals of the projects are to develop thromboresistant surfaces based upon (1) controlled release of heparin incorporated into a surface layer of polymer and (2) controlled release of a platelet-inhibiting agent from a polymer layer. Fine micronized particles of heparin and imbedded heparin-TDMAC complex have been incorporated into poly lactic acid (PLA). Daily release rates of 0.3% and 0.16% of the heparin have been measured. A hydrophobic anti-platelet drug has been incorporated in PLA and found to form clear films. Baseline studies in dogs have shown occlusion of 3-5 mm Goretex and polyester arterial grafts in 6-18 months. First in vivo measurements (in unheparinized dogs) for the heparin-releasing PLA, coated on woven polyester patches and tested 8 hrs. to 3 days in the vena cava, show it to develop much less thrombus than Goretex and polyester control patches. Patches coated with PLA releasing the anti-platelet drug show no adherence to the covering clot, which is attached only at the suture line.